Defense Intelligence Reference Document The Role of Superconductors In Gravity Research

UNCLASSIFIED/ ,'l"e" Cl"l"!e1,it tl!!L e11t I
except possibly for his proofreading skills. Strangely, the only persons who contacted
Podkletnov in the mid-1990s about the paper were the Italian theoretical physicist G.
Modanese and this author. Podkletnov claimed he had never heard of the work of Li and
Torr prior to publishing the paper.
According to the 1992 paper, the essence of his experiment was the high-speed
rotation of a relatively large (14.5-cm diameter x 6-mm thick) YBCO sintered ceramic
superconducting disk in the vapors of liquid helium (LHe). The disk was levitated by
Meissner repulsion over a large support electromagnet immersed in LHe that was
powered by a variable-frequency supply from 50 Hz to 106 Hz. At the diametrical
periphery of the disk were positioned two additional but smaller electromagnets also
powered by variable frequency supplies. These two "rotational" electromagnets were
used to spin the disk in some unspecified manner. A small nonconducting, nonmagnetic
test mass was suspended from an analytical balance about 15 mm from the top of the
disk. Subsequent information from Podkletnov indicated that to obtain the maximum
stable test sample weight loss of about 0.3 percent, the optimum conditions required
operation of these two electromagnets at frequencies of 105 Hz and disk rotational
speeds of several thousand rpm.
Apart from the difficulty believing, on purely theoretical grounds, that such an
enormous weight loss was possible, there was considerable doubt about the validity of
the observations based on experimental issues. Among many other concerns, a few
comments regarding the cryostat are in order. The only information on the physical
configuration of the experiment is given in the sketch provided in Reference 15.
Referring to that figure, it is difficult to believe the only thing separating the vapors of
LHe in the cryostat from the laboratory atmosphere was a thin plastic film. Ordinarily,
so much water vapor and other gases would have condensed on the outer surface of
the film as to render it completely opaque, thus making the observation of the disk
extremely unlikely. If the cryostat was actually designed roughly per the sketch in the
article, the LHe would be boiling so vigorously that it would rupture any film unless
adequate He gas escape was provided. As pointed out by dePodesta (Reference 23),
thermal currents and buoyancy changes above such a cryostat would be so severe as to
render the determination of the weight of a test mass suspended only 1.5 cm above the
disk (and therefore only a few mm above a separating film covered with ice) virtually
impossible. This was an entirely unsatisfactory cryogenic design for the purpose.
Important issues such as how the disk was balanced, how it was prevented from
rupturing at high speeds, how much power was used to operate the coils, and what
means were employed to prevent the balance from being affected by the magnetic
fields from the coils were not addressed in the article. Nevertheless, the article caused
experimentalists around the world to try to duplicate the essence of the experiment,
generally in an overly simplified manner. All started out using the less costly LN2
approach with either fixed or rotating permanent magnets and small ( ~ 2- to 3-cm
diameter) disks purchased commercially. Several researchers, including Gonnelli at
Turin Politecnico (Reference 24), Woods at the University of Sheffield (Reference 25),
and this author witnessed very slight apparent weight changes while the disk was
passing through its critical temperature, Tc. However, in most cases, the effect was so
close to the noise that further experimentation was not considered. At a private
unpublished meeting (see below) hosted by Professor R. Gonnelli at the Turin
Politecnico in April 1999, however, Podkletnov made it clear that unless the exact disk
formulation was followed, high-frequency magnetic fields were employed (not
5
UNCLASSIFIED//FQA arrI@ItllL ~:!I! enc I